Yellow River

On its way, the river crosses a land covered in fine, dusty soil.

The soil washes into the river and turns the water yellow.

The Yellow River crosses the Loess Plateau, a high land covered with up to 300 meters of fine soil that was carried there by the wind. This soil is easily worn away, and the river carries millions of tons of it every year.

The tiny grains are bits of minerals called mica, quartz and feldspar, and they give the river its yellow color. In the past, the river carried more than 1.6 billion tons of sediment a year, making it one of the muddiest rivers in the world.

NASA's Scientific Visualization Studio describes the plateau the river crosses as blanketed with up to 300 m of fine, wind-blown soil (loess). It erodes easily, and millions of tons are carried away by the river every year. The Earth Observatory attributes the yellow color to fine particles of mica, quartz and feldspar picked up from the soft, silty plateaus.

Historically, the river's sediment load exceeded 1.6 billion tons a year, earning it a reputation as one of the muddiest rivers in the world. That load also explains its restless lower course: few rivers have silted up, burst their banks and changed course as often.

Where the river meets the sea, the mud settles and builds new land.

This land is called a delta. Its shape changes again and again.

When the Yellow River reaches the Bohai Sea, much of its sediment drops to the shallow sea floor. If there is enough of it to beat the waves and tides, it builds new land. NASA satellite images from 1979 and 2000 show the delta pushing out into the sea like a giant hook, adding several hundred square kilometers of land.

The river's mouth has moved at least a dozen times since 1855. In 1976 and again in 1996, people moved the river's last stretch to a new channel, and new land quickly grew at the new mouth.

The delta is unusually dynamic: sediment dropped on the shallow bottom builds land wherever it outpaces wave and tidal erosion. Landsat images from 1979 and 2000 show it expanding into the Bohai Sea like a giant hook, adding several hundred square kilometers to China's coast. Over the past two thousand years, the delta wandered up and down several hundred kilometers of coastline.

The mouth has shifted (avulsed) at least a dozen times since 1855. The last two major changes were engineered, in 1976 and 1996, mainly to control flooding and protect coastal development; after 1996 a new peninsula had formed to the north by 1999, while the shoreline around abandoned channels retreated.

The muddy shores near the river's mouth are full of food for birds.

Many birds stop there to rest and eat on their long trips.

The Shandong Yellow River Delta Wetland is one of nineteen parts of a UNESCO World Heritage Site: the Migratory Bird Sanctuaries along the Coast of the Yellow Sea-Bohai Gulf of China. Together, these places lie in the largest intertidal wetland system in the world and support more than 400 kinds of birds.

They are an important stop for birds flying along the East Asian-Australasian Flyway, a migration route. The mudflats, marshes and shallow waters are very rich in food and give many kinds of fish and crustaceans a place to breed and grow.

UNESCO lists the Shandong Yellow River Delta Wetland among the nineteen component parts of the Migratory Bird Sanctuaries along the Coast of the Yellow Sea-Bohai Gulf of China, inscribed through Phase I (2019) and Phase II (2024) of a phased nomination. The property lies in the largest intertidal wetland system in the world, one of the most biologically diverse, and supports more than 400 bird species.

It is an irreplaceable hub on the East Asian-Australasian Flyway, which UNESCO calls one of the world's most important flyways and arguably the one most at risk. Its intertidal mudflats, marshes and shallow waters are exceptionally productive, providing spawning and nursery habitat for many fish and crustacean species.

Today the river carries much less mud than before. Dams and new trees hold the soil back.

So the delta grows more slowly, and people work to protect its wetlands for the birds.

By some estimates, the Yellow River now carries only a tenth of the sediment it carried in the 1960s. Dams, projects to stop soil erosion and new forests upstream trap much of the water and sediment, so less new land is built at the delta.

UNESCO says that people have changed many of the region's tidal wetlands, and that the birds also depend on reed beds and groves around the protected areas. Protecting and restoring those places matters as much as the sanctuaries themselves.

NASA's 2021 Earth Observatory story reports that, by some estimates, the river delivers only a tenth of its 1960s sediment and about half of its 1980s load, because dams, erosion-control and reforestation projects upstream trap water and sediment. Meanwhile parts of the delta are sinking: up to 10-20 mm a year from natural compaction in many areas, and hundreds of millimeters a year near some pumps, while sea level rises about 4 mm a year.

UNESCO notes that human activity has transformed many of the region's tidal wetlands, calls for effective measures to halt major threats and restore key bird habitats, and stresses that the wider coastal habitats the birds depend on, such as reed beds and groves, need protection too.